Aborted take off due to not closed cargo doors. How this will be signalled? A hypothetical situation (I know that it is very unlikely to happen in real). When closing cargo doors, a piece of fabric from the luggage carrier's uniform stick in between. The cargo door is actually closed (no real danger), but the latching sensors are sending a misleading signals.

How this will be communicated in the cockpit? What visual or audio signal will be used / emitted in the cockpit to inform the crew about the reason? Is there any specific light or button as an endpoint for cargo doors sensor? Is there any specific sound?

How will the crew communicate to the tower the reason for an aborted take off (what kind of message, who will do this -- flying pilot, non-flying pilot)?

Clarification: This question is for the sake of the story that I am writing. It (both story and the question) involves Boeing 777 taking off from LHR in August 2014.

Aborted take of is due to a misleading information coming from cargo doors' sensors that reveal a possible problem only during take-off, not before (i.e. during taxi). The doors are actually closed (no real danger posed after check). But there's a tiny piece of fabrics from cargo loader's uniform stick in between doors. This question is a follow-up or alternate version of this question. Here I'd like to know what happens, if such situation will be detected before V1. In linked question I am asking about the same situation detected after V1 or shortly after take-off and thus after such aircraft returns safely to the airport and clears the runway.

I am aware that most airline experts will say that such situation is not possible at all. I am, on the other hand, a system designer and I know that such "ghost" situations of "neither 0 nor 1" sometimes do happen. But, for the sake of this question, if you feel uncomfortable with such reason -- let's assume that take-off was aborted due to any other reason, i.e. engine failure. I belive that such reason has similar severity as the need of checking whether cargo doors are really closed due to fact that on-board computer provides misleading data.

I'd lilke to underline that this is purely hypothetical question. I am aware that while such questions are sometimes hard to answer, they're in general quite welcomed in this site and are not off-topic.
You will typically get a DOOR OPEN alert displayed on the EICAS system.  A competent crew would have spotted such a discrepancy before pushback.